Accommodative and tonic convergence and anatomical contracture in partially accommodative and non-accommodative esotropia.

PURPOSE

To compare accommodative convergence, tonic convergence, and anatomical contracture quantitatively in partially accommodative esotropia vs non-accommodative esotropia.

METHODS

Patients with an esotropia who had undergone surgery under general anaesthesia were evaluated. They were divided into two groups: 17 patients had partially accommodative esotropia and 15 patients had non-accommodative esotropia (basic esotropia). We supposed that the total esodeviation (Eso) was composed of three components: accommodative convergence (AC), tonic convergence (TC), and anatomical contracture (AnC). We measured the preoperative angle of esodeviation with (AC) or without glasses (Eso) in awakening state at 1/3 m and the preoperative esodeviation under general anaesthesia (AnC). TC was calculated by the formula TC = EsoD-AC-AnC.

RESULTS

The average ratios of TC/Eso, AC/Eso and AnC/Eso were 46%, 32%, and 22%, respectively in the partially accommodative esotrope group, and 28%, 1%, and 71%, respectively in the non-accommodative esotropes. These differences were significant for AC/Eso and AnC/Eso (p < 0.0001) but not for TC/Eso (p = 0.15).

CONCLUSIONS

Among the three components, tonic convergence was responsible for a larger portion of esodeviation than anatomical contracture in partially accommodative esotropia, whereas anatomical contracture played a greater role in the non-accommodative esotropia group.